Large area multifunction active arrays are used in radar and communication systems. In radar systems, the active arrays use electromagnetic waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain. Active array antennas are typically electrically steerable. Thus, unlike mechanical arrays, active arrays are capable of steering the electromagnetic waves without physical movement. As active array antennas do not require systems for antenna movement, they are less complex (e.g., no moving parts), are more reliable, and require less maintenance than their mechanical counterparts. Other advantages over mechanically scanned arrays include a fast scanning rate, substantially higher range, ability to track and engage a large number of targets, low probability of intercept, ability to function as a radio/jammer, and simultaneous air and ground modes.
Active array antennas include a number of transmit/receive (TR) modules for transmitting and receiving electromagnetic waves, and a number of radiating elements. Typically, there is one TR module for each antenna radiating element. Each TR module generally includes a power amplifier (PA) for transmitting electromagnetic waves, a low noise amplifier (LNA) for receiving electromagnetic waves, a phase shifter for changing phase angles of the electromagnetic waves and transmit/receive (TR) switches for toggling transmit or receive functions. An example of a conventional active array antenna architecture including multiple conventional TR modules can be found in U.S. Pat. Publ. No. 2008/0088519, the entire content of which is expressly incorporated herein by reference. Other examples of conventional TR modules can be found in U.S. Pat. No. 5,339,083 to Inami and U.S. Pat. No. 6,992,629 to Kerner et al., the entire content of each reference document is expressly incorporated herein by reference.
Conventional TR modules for active arrays dissipate substantial power and include expensive components that contribute to antenna weight. Passive electronically scanned arrays (ESA) that use MEMS and varactor type phase shifters dissipate little power but have a high noise figure due to losses associated with the phase shifters and the associated RF feed network. In conventional active arrays, the noise figure is set by the LNA and loss in the path before the LNA. However, the collective power dissipation associated with conventional TR modules and their LNAs is often too high to meet the requirements of new applications. Future applications of active array antennas require reduced power dissipation, reduced cost, and reduced weight.